1. Field of the Invention
The application relates to an electronic module. More particularly, the invention relates to a stacked-type electronic module.
2. Description of Related Art
With the advancement of science and technology, human beings tend to rely on electronic devices to a greater extent. To meet the requirement for light weight, slimness, compactness, and great operational performance, various handheld electronic devices, such as ultra mobile personal computers (UMPCs), tablet PCs, pocket PCs, personal digital assistants (PDAs), cell phones, and notebook PCs, have been developed.
However, due to the increasing demands for operational capabilities as well as other functions of the handheld electronic device, it is no longer sufficient to hold electronic components in the electronic device with an individual circuit board. Hence, a design of two stacked circuit boards has been applied to electronic modules in some electronic devices, so as to increase the number of the electronic components held by the circuit boards. FIG. 1 is a schematic cross-sectional view illustrating a conventional electronic module with a stacked structure. With reference to FIG. 1, the conventional electronic module 100 has two circuit boards 110 and 120. The circuit board 110 has a plurality of electronic components 112 thereon, and the circuit board 120 has a plurality of electronic components 122 thereon. Since the operational efficiency of the electronic components 112 and 122 continues to increase, electromagnetic waves that are generated during the operation of the electronic components 112 and 122 need to be properly shielded, so as not to affect antennas or other electronic components. Hence, the electronic component 112 is covered by a conductive fence 132 and a conductive cover 134, and the electronic component 122 is covered by a conductive fence 142 and a conductive cover 144. The circuit board 120, the electronic component 122 on the circuit board 120, the conductive fence 142 on the circuit board 120, and the overlying conductive cover 144 are then directly stacked onto the conductive cover 134.
To prevent the possible collision and the resultant damages to the electronic components 112 and 122, the conductive covers 134 and 144 are not allowed to be in contact with the electronic components 112 and 122. For instance, if the maximum height of each of the electronic components 112 and 122 is 1.2 mm, respectively, the height of each of the conductive fences 132 and 142 is required to reach at least 1.3 mm, respectively. A thickness of each of the conductive covers 134 and 144 is 0.1 mm, respectively, a thickness of each of the circuit boards 110 and 120 is 0.7 mm, respectively, and a thickness of an adhesive layer 150 between the circuit board 120 and the conductive cover 144 is 0.1 mm. Thereby, the overall thickness of the electronic module 100 reaches 4.3 mm. That is, the overall thickness of the electronic module 100 is determined by adding the thickness of the adhesive layer 150 to the total thickness of the individual circuit boards 110 and 120 and the overlying components. As a result, it is difficult for the electronic device having the electronic module 100 to satisfy the requirement for compactness and light weight.